public class TestBinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val=val;
        }
    }

    public TreeNode createTree() {
        TreeNode A=new TreeNode('A');
        TreeNode B=new TreeNode('B');
        TreeNode C=new TreeNode('C');
        TreeNode D=new TreeNode('D');
        TreeNode E=new TreeNode('E');
        TreeNode F=new TreeNode('F');
        TreeNode G=new TreeNode('G');
        TreeNode H=new TreeNode('H');

        A.left=B;
        A.right=C;
        B.left=D;
        B.right=E;
        C.left=F;
        C.right=G;
        E.right=H;

        return A;
    }

//    前序遍历
    void preOrder(TreeNode root) {
        if(root==null) {
            return;
        }
        System.out.print(root.val+" ");
//        递归遍历左子树
        preOrder(root.left);
//        递归遍历右子树
        preOrder(root.right);
    }



//    中序遍历
    public void inOrder(TreeNode root) {
        if(root==null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }




//    后序遍历
    public void postOrder(TreeNode root) {
        if(root==null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

//    获取树中节点的个数
    public int size(TreeNode root) {
        if(root==null) return 0;
        int ret=size(root.left)+size(root.right)+1;
        return ret;
    }

    public static int nodeSize;
    public void size2(TreeNode root) {
        if(root==null) return;
        nodeSize++;
        size2(root.left);
        size2(root.right);
    }

    /*
    * 如何求叶子节点的个数
    * 1.子问题的思路（整棵树的叶子结点个数=左子树的叶子结点+右子树的叶子节点
    * 2，遍历思路（以某种方式遍历这棵树，只要发现是叶子，就++）
    * */
//    递归
    public int getLeafNodeCount(TreeNode root) {
        if(root==null)return 0;
        if(root.left==null && root.right==null) return 1;
        return getLeafNodeCount(root.left)+
                getLeafNodeCount(root.right);
    }
//      遍历
    public int leafCount;
    public void getLeafCount2(TreeNode root) {
        if(root==null) return;
        if(root.left==null && root.right==null) leafCount++;
        getLeafCount2(root.left);
        getLeafCount2(root.right);
    }

    /*
    * 判断第k层有多少个节点
    * */
    public int getKLevelNodeCount(TreeNode root,int k) {
        if(root==null) return 0;//空树
        if(k==1) return 1;
        return getKLevelNodeCount(root.left,k-1)+
                getKLevelNodeCount(root.right,k-1);
    }

    /*
    * 求当前树的高度（最大深度）
    * =max（左子树最大高度，右子树最大高度）+1
    * */
    public int getHeight(TreeNode root) {
        if(root==null) return 0;
//        int leftHeight=getHeight(root.left);
//        int rightHeight=getHeight(root.right);
//
//        return leftHeight>rightHeight? leftHeight+1:rightHeight+1;

        return getHeight(root.left)>getHeight(root.right)?
                getHeight(root.left)+1:
                getHeight(root.right)+1;

    }

    /**
     * 遍历二叉树，找到val所在的节点
     * */
    public TreeNode find(TreeNode root,char val) {
        if(root==null) return root;
        if(root.val==val)return root;
        TreeNode ret= find(root.left,val);
        if(ret!=null)return ret;

        ret= find(root.right,val);
        if(ret!=null)return ret;
        return null;
    }
}
